Fluid Drive vs. Semi-Auto Transmission

I own a 1950 Dodge Coronet with the standard 3-speed manual transmission hooked up to the Dodge fluid coupling. This is the standard "fluid Drive" configuration as opposed to any of the Chrysler so-called semi automatic M4/M5/M6 transmissions offered during the '40s and early 50's. Through the years, I have found that there is much confusion among the various transmission types, and after finding an incomplete and inaccurate article on Wikipedia. I re-wrote the Fluid Drive entry to provide complete and accurate information on the different transmission/driveline types. Please see http://en.wikipedia.org/wiki/Fluid_Drive, or type type "fluid drive" in the query box on the Wikipedia main page to see the article.

I appreciate all the information on this page relative to the proper type of fluid for the fluid coupling, and am leaning toward Jon Robinson's recommendation of 10W non-detergent motor oil, which is readily available at my local NAPA store (Massachusetts). Would like to hear more from members concerning their success/failures on servicing the fluid coupling unit. Mine seems OK, with some slippage on start, but once the car is underway, slippage seems minimal. What is considered "normal" slippage for these units? Obviously there has to be some at startup.

Thanks is advance for any advice.

"How much slippage is normal?"...

Good question... I've never seen a spec on it in any of my factory shop manuals... they speak vaguely about "the engine racing under load" being an indication of low or improper fluid level in the fluid coupling...

There is going to be more "slippage" than we are used to with the "modern" torque-convertor automatics that have been around since the mid 1950's... this is because the first generation Fluid Coupling is a "direct" 1:1 coupling ( almost); there is no torque multiplication happening there...

That is why FD cars take-off more slowly than the same vehicle outfitted with a "dry clutch", even when starting in low gear... although starting in low, and "marching through the gears" provides the best "performance" when driving the "Fluid-Drive + 3-speed" combo... the higher gear you take-off in ( 2nd, or 3rd), the more "slippage" there's going to be until the engine and dirveshaft speeds equalize...

The other difference between FD/non-FD cars was that Chrysler Corp. found that they could equip their FD cars with "taller" ring & pinions, and achieve better highway cruising (and slightly improve the fuel economy) than was possible with a "dry clutch". The "slippage" of the Fluid Coupling allowed the engine to rev-up into its peak torque band ( about 1400-1600 RPM) on take-off, whereas the taller rear would've made the same dry-clutch car a "dog" on hills and in urban driving...

This practice continued into the automatic transmission era: auto-tranny cars still have taller gears than stick cars...

My '41 De Soto De Luxe has a 228 flat-head six, dry clutch, and 3-speed stick. It came with a 4.1 rear. When outiftted with Fluid Drive and 3-speed, they used a 3.9 rear, and when equipped with the four-speed semi-auto, they used a 3.54 rear...

From all the advertising hype I've read about the early "automatic drive" systems, the gimmick was to "relieve the driver of the tedious chore of shifting gears"... ( oh pu-LEEZE ! <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />)

This was also the era of the almighty patent... GM led the way with the only true "automatic" transmission ( system of planetary gears, bands and disc clutches; can up-shift under load w/o interruption of power to wheels; requires no further input from driver after selection of driving range) in 1940: the Hydramatic.

Other makers either bought Hydros from GM, or futzed around with their own make-shift semi-autos until they either caved-in and bought Hydramatics from GM, or developed their own auto-trannies...

Other semi-autos included Hudson, with their Drive-Master; Packard and their Electromatic Clutch;

(Both of these had "automatic" vacuum-operated clutches, which worked off intake vacuum, but the driver still had to operate the shift lever, or put the vehicle in Overdrive and enjoy the "automatic" shifting of the OD unit). Nash also offered a vacuum clutch into the '40s.

Studebaker and Lincoln were the only non-Chrysler marques to combine a fluid coupling with a manual/semi-automatic gear box: both were offered in '42: Stude offered "Turbo-matic Drive" (a fluid coupling + 3sp OD); Lincoln offered "Liqui-Matic Drive" ( also a fluid coupling + 3 sp OD). They were not continued after the War.

Chrysler was the only company ( besides REO) that had a gear-box that actually shifted gears "by itself"... the M-4 Simplimatic did this via a governor, relays, solenoids, and vacuum servos; after the war, Chrysler revised this into the M-5 Hydraulically-operated transmission, using an internal oil-pump, valves and pistons to shift the gears. The control system was revised in '49, eliminating the relay, but the unit remained largely unchanged through its final season: 1954.

The biggest handicap of the semi-auto (aside from the complicated control system) was having to take one's foot off the gas pedal and wait for the engine to wind-down and the transmission to shift its sliding gears ( actually a sleeve)... Dave Duricy at DeSotoland has coined this: "wait for the klunk!"... maybe not such a handicap for the wheezy old flathead six, but a real damper on those hot new Firepower and Firedome Hemis that were going under the hood.

A modest improvement was the addition of the "Fluid-Torque Drive", which utilized a true torque-multiplying Torque Converter in place of the old 1:1 Fluid Coupling...

It would seem that the various non-GM makes did what they could "in-house" to offer some sort of "automatic" drive, but eventually the superior performance and reliability of the "true" automatic transmission proved itself, and Fluid Drive went the way of the flathead engine...

To its credit, Chrysler Corporation evetually developed very good automatic transmissions, the 2-speed Powerflite and 3-speed Torqueflite; just a little later than most of the other big marques...

And, a bit more trivia: A man by the name of Radcliffe demonstrated his "revolutionary new transmission" for Studebaker around 1916... it consisted of two sets of turbine vanes encased in an aluminum housing filled with oil; one set of vanes was turned by the engine, the other set "reacted" and was connected to a conventional clutch and driveshaft. The unit was tested with some sucess, but ultimately deemed impractical and was shelved.

Among the Studebaker engineers in on the testing were a certain Carl Breer and Fred Zeder, who went on to become two-thirds of Chrysler Corporation's engineering triumverate: "The Three Musketeers"... it is interesting to note how many similarities there are between Mr Radcliffe's "transmission" of 1916, and the Fluid Drive that graced Chryslers, De Sotos, and Dodges beginning in 1939...

I have just read your article at Wikipedia, and it is pretty-much on the mark, and makes the Fluid Drive concept pretty simple for the layman...

I will definitely agree to the "confusion" caused by Chrysler's flagrant use of the term "Fluid Drive", but then they really flogged the "Floating Power" gimmick too... the rubber front motor mounts of my 1960 Chrysler Windsor STILL had the words "Floating Power" molded into them !!!

This "Underdrive" term is another source of confusion... I have seen it in several different service texts, and I believe some ad text too... I think that term is purely a product of Chrysler's Madison Avenue adverstising writers...

Since Overdrive trannies were becoming popular, I think some advertising "genius" thought that the term "Underdrive" was a good monniker for the new semi-automatic...

However, from a functional standpoint, ALL of Chrysler's semi-autos ( M-4 thru M-6, Except for the Chrysler 8, in '41) were four-speed manual gearboxes that were "divided" into two operating ranges: Low and High. The only "direct drive" was High Range, high-gear ( fourth gear, top gear, whatever you want to call it). All other speeds were running through countershafts and reduction... I guess that would make it "underdrive", but that doesn't make it much different from any other manual transmission: until the age of the five-speed OD tranny, all gears except "top gear" were "underdrive"...

(The exception of the '41 Chrysler 8: the semi-automatic in these cars was actually a fluid coupling, plus 3-speed overdrive tranny; these were the last Chrysler products to feature Overdrive until 1949. The Overdrive option was dropped after 1940 for the Chrysler six and all De Soto and Dodge.)

Chrysler Corp. was at its engineering peak during the 1920's and 1930's... it continued to have its engineering triumphs after 1940, such as the Hemi, but it would seem that after the Airflow debacle, senior management called for a much more conservative approach to car building... ( Carl Breer felt the return to "conventional automotive design" was a real step backwards for Chrysler...)

There is no question as to the rock-solid quality and reliability of Chrysler Products built between 1935 and 1955, but they were not particularly known for their styling or their performance...

But all of that seemed to change in 1955...

My 1950 Wayfarer has the standard 3 speed with fluid drive. We rebuilt the engine 3+ years ago. All we did to the fluid drive unit was drain it and refill with Dexron tranny fluid... at the time, there were postings indicating that this was an OK fluid to use. Since then, I've read that it might lead to failure of the seals. However, our unit works perfectly and I've never changed out the fluid. It never leaks a drop and I don't note any slippage at all... it just shifts very smoothly with no clutch chatter whatsoever. I love the low-end torque this engine/tranny delivers! I can pull a fairly steep hill and accelerate in 3d geat @15 mph! I did subsequently have the tranny removed and all new seals/gaskets installed. It also works great. I use SAE 80-90 fluid in the standard tranny and it also seems to work great... no hard shifting, even in cold weather (and it does get cold here in Kansas).

Is is true that the higher the road speed when the driver lifted his foot to await the 'clunk', the longer it took for the shift to occur? I read this once and, if true, that would be another performance-robbing characteristic of the semi-automatic/Fluid Drive combination.

There's a section in the D34 shop manual about slippage. After talking about how it is "subjective," the manual details a test: put a tachometer on the engine, warm it up, set the parking brake and hold down on the service brakes so the car can't move. Put it in third gear, floor the engine and let it stabilize as fast as it will go. "Normal" top engine speed under this condition is supposed to be "about" 1200 RPM. I don't know what any of this could prove, other than whether the engine is in good tune and there's enough fluid in the coupling, but apparently it was of enough concern in 1950 for somebody to take the trouble to detail this in the manual. (Maybe this was a "scientific test" you were supposed to perform so that you could tell your customer that his car either was or was not in good shape....

One thought is that this "test" might be a way to compare results with different fluids in the coupling: if we know that 1200 RPM was expected with whatever fluid Chrysler was hawking for the cars back then, one could then compare results with 10W oil, hydraulic fluid, Mazola, or whatever--assuming anyone in their right mind wanted to go through the business of draining and refilling the coupling, multiple times over. Aristotle observed that it is the mark of an educated person to bring to each situation the degree of precision appropriate to it--and that may the point here.

Slippage or no slippage, I do know that my dear mother never would have learned to drive in 1950 on a "dry clutch," but managed--after a fashion, that is, accelerating very slowly--with the fluid drive Dodge, and later with a 1953 Chrysler with the M6....And a bit of sedate slippage seems to go together, somehow, with K. T. Keller's remark about the importance of making cars where one could wear a hat while driving....

Well, short answer being "yes", it 's like this ( sort-of)...

With the M-5 ('46-'48) and M-6 ('49-'54) "Hydraulically-operated" transmissions, when starting off from a stop, there is no oil pressure in the transmission, as the tranny oil pump is driven from the tranny output shaft/driveshaft. As the vehicle picks-up speed, the oil pump begins to function, but until the governor opens its points, the kick-down solenoid is energized, and all pump-pressure is bypassed back into the tranny case.

When the vehicle speed reaches about 12-14 MPH (Hi-range), the governor points open, and the solenoid is de-energized, closing the by-pass valve: now the oil-pump pressure builds-up behind the main shifting piston, which moves forward in its bore, compressing a large heavy spring against the shifter fork... but the tranny is still in low-speed.

When the driver takes his foot off the gas, the engine (and tranny input shaft) winds down, eventually reaching a low-enough speed where the input-shaft "synchronizes" with the rest of the main-shaft cluster, and that spring is able to move the shifter sleeve forward all the way, completing the shift into "Hi-gear"...

This is very similar to trying to drive a manual shift car without using the clutch to change gears: you can upshift, but the gears will not (easily) mesh into the next higher gear until the input shaft speed matches-up with the rest of the spinning stuff... since the M-5/M-6 free-wheels when in low-speed, the input shaft almost has to come to complete rest for the gears to shift... thus the low idle-speed requirement.

The length of time between releasing the gas pedal and the "klunk" of the completed upshift is more or less determined by how much the engine has to slow down ( these are all long-stroke engines, with lots of inertia), how good the compression is ( better compression= quicker engine rev-down), where the idle speed is set ( the higher the idle speed, the faster the car must be accelerated in low speed)...

The main point to remember is that the Chrysler semi-autos are sliding-gear manual boxes that are modified to change gears "automatically"... you still have the dynamic of having to wait for the engine to rev-down between upshifts...

And there was really no way to speed-up the process, except perhaps by manually clutching during up-shift, to "help" the tranny shift faster... there's really no way to "speed-shift" a MoPar semi-auto...

Yes, it was a performance handicap by the time the FirePower Hemi came along...

Frank,

Your excellent description of the M5/M6 upshift operation got me to thinking some more about it. It seems to me that the engine speed does not have to drop to idle speed or "almost complete rest" in order for the upshift to occur. Instead, I think the direct speed clutch synchronizes when the engine speed drops to the point where it matches the speed of the transmission mainshaft. For example, if the accelerator is lifted when the car is in 3rd gear at an engine speed of 1750 RPM and a main (and propeller) shaft speed of 1000 RPM, the engine slows down until its speed drops to about 1000 RPM (assuming that the car doesn't lose any speed during the shift), at which point the transmission shifts into 4th gear.

If the engine actually did drop to idle speed during every upshift, I'd expect there would be deceleration of the car and re-acceleration of the engine when engaging 4th gear at higher road speeds (30-45 mph), since the free-wheeling is bypassed in that gear. In my experience, that isn't the case.

Comments?

Doug

Doug,

You're correct in terms of how this would work in shifting a manual tranny w/o a clutch...

But the Fluid Drive semi-auto was set-up so that the driveshaft "Free-wheeled" when the tranny was in lower speed of either driving ranges: the rear-wheels would NOT drive the engine until the tranny had upshifted into high-speed. They were designed this way so that the car would glide along while the upshift was taking place; also to prevent there being "reverse strain" ( engine-braking loading) on the gears that would prevent it from shifting out of low-speed...

(During the downshift process, there's an interrupter switch that momentarily shorts the ignition, to relieve the strain on the gears and permit downshift to occur)

This is why when push-starting an M-5 / M-6, you have to get the car going about 20 mph, put in the clutch for a few seconds ( while the tranny up-shifts ), then let the clutch out again, and THEN the rear wheels will turn the engine.

With the earlier vacuum-shifted tranny (M-4,'41-'42), a "lock-out control" was provided for "emergency starting"... it looked just like the Overdrive lock-out control from the '39-'40 Chrysler/De Soto, and manually shifted the tranny into high-speed, for push-starting...

The whole semi-auto gimmick was kind of neat for its day...

Even Mercedes-Benz had a variation: Hydrakak - fluid-coupling & semi-auto... YIPE !

I really learned this stuff the hard way when my '48 NYer tranny ate a countershaft-gear during my junior year of college, and I had to fix it as it was my daily driver... I tried using the M-6 from my '50 NYer, found it wouldn't fit w/o shortening the driveshaft, and eventually wound-up robbing the necessary parts from the M-6 to make the M-5 work again... this was in summer of '88, before the wonderful Internet or on-line antique car forums...

My biggest stumbling block was trying to think of the semi-auto in terms of a "true" automatic tranny (bands, planetaries, clutches; the Model T Ford has all of these - it only lacks a fluid coupling and automatic control system!), which has NOTHING to do with the Chrysler semi-auto... Once I began to approach it as an evolution of the sliding-gear manual tranny, the whole thing began to make a lot more sense... it's still kind of a Rube Goldberg way to shift gears, but at least I finally understood the principles and was able to get my car working again...

( I'm not in any big hurry to have another one for a driver... <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />)

Maybe I'll take on Packard's Electromatic Clutch or Hudson Drive-Master for my next lesson in automotive self-torture ! <img src="http://forums.aaca.org/images/graemlins/smirk.gif" alt="" />

Hi Frank,

I agree about the importance of the free-wheeling feature in allowing the car to coast and the engine to slow down to permit the upshift. What I can't get around is that, in engaging 4th gear, the direct speed clutch sleeve essentially couples the transmission input shaft (at the main drive pinion) to the transmission output shaft, completely bypassing the free-wheeling gear. When the sleeve "synchronizes" the input and output shafts, they have to be turning at just about the same speed.

Engine idle speed corresponds to around 10-12 mph in 4th gear so if the upshift actually required that the engine speed drop to idle, an upshift at say, 35 mph, would abruptly force the engine to triple its speed. The fluid drive would certainly absorb some of the shock of such a speed mismatch but, as I mentioned above, it doesn't feel to me as though the momentum of the car is re-accelerating the engine after an upshift.

P.S. I've always wanted to drive a Hudson with Drive-Master just to see what it's like. What scares me are the circuit diagrams for the Bendix Electric Hand pre-selective gear shift that Hudson and other used in the mid-30's.

Doug

Doug,

I think the feeling (or lack there-of) of the engine speeding-up due to vehicle momentum after the upshift has completed is due to the "sponginess" of the Fluid Coupling...

The input shaft may not come completely back to idle, I think it just has to "get close enough" for the synchros to do the rest...

The shop manuals are pretty specific about keeping the idle speed setting low for proper upshift...

From an operational standpoint, I found that if I didn't take my foot completely off the gas pedal, the tranny would not upshift... ( you couldn't just "lighten you foot" on the gas pedal, as you would when trying to "help" a tired auto-matic upshift w/o slipping)... I also found this to be the case with the very first semi-auto MoPar I drove: a '48 De Soto Custom that I was thinking of buying... that was a couple of years before I finally wound-up with the '48 New Yorker...

Also, when I was trying to get my '48 New- Yorker working after cannibalizing a '50 M-6 tranny for parts, I was trying to test the tranny for sucessful operation while the rear-end of the car was up on jackstands... try as I might, I could not get the tranny to upshift while running on jacks... the rear wheels ( driveshaft & rear pump too) simply didn't have enough of their own momentum to carry the system through the 2 to 4 second up-shift process... I finally did get it to upshift once, after running things up to nearly 30 MPH in the low-speed of Hi-range... when the upshift did occur, it was frighteningly violent <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" />...

I finally decided to just expend the effort to get the car back on the ground and do a road-test: everything functioned just fine - the vehicle momentum is definitely part of the upshift equation...

And, as I'm writing all of this, I am nearly 20 years-removed from this semi-automatic odyssey with my beloved C-39... so some details are a little foggy...

I think I may have to get that car back on the road just so I can re-acquaint myself with the everyday joys of Presto-Matic Fluid Drive... <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />

Hi Frank,

Thanks again for the useful information. I think I'm going to take my '48 Windsor out on the road with a tachometer hooked up and see what I can observe during an upshift.

Yes, I've also tried upshifting with the car on jackstands and, as you say, it's kind of scary...feels like the car is going to jump off the stands and crash through the back wall of the garage.

Doug

I'd be interested in what you find out with the tach...

<img src="http://forums.aaca.org/images/graemlins/cool.gif" alt="" />

Hi Frank,

Here?s what I did and what I observed:

After a few trial runs, I made three 3rd-to-4th gear upshift tests at road speeds of 15, 25, and 35 mph. In each test, I brought the car to a steady road speed, noted the speedometer and tachometer readings, then lifted the accelerator and watched the tach. The results were (in mph/rpm(before)?.rpm(after), where the rpm(after) value was the reading at the instant that the transmission ?clunked? into 4th gear:

15/1050?.550

25/1800?.950

35/2500?.1300

The accuracy of this kind of dynamic test depends, of course, on the damping of the tachometer, but it appeared to me that the tach was following the speed of the engine pretty well, judging by the sound of the engine. In each test, the tach dropped to about 50 rpm below the ?after? rpm value and then ?locked in? at the ?after? rpm value at the instant the transmission shifted. My tune-up tachometer is 1500 RPM full scale on the Low RPM range so I have some confidence in the readings.

Sadly, I also have to report that my transmission failed the following day <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" />. Sunday was a beautiful day so I decided to drive the Chrysler up to Santa Barbara from Los Angeles to visit a friend from my college days. The car ran beautifully going up and while I was there <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />. However on the return trip, the transmission suddenly came out of 4th gear <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" /> and now will not upshift into either 2nd or 4th gear. Thanks to AAA, the Chrysler and I are now home again. I?ve checked out the electrical controls and they seem to be working properly so now the car will have to go up on the jackstands again to see if the transmission hydraulics are the problem. Maybe next weekend?.

Doug

Doug,

Thanks for posting your data !

I'm sorry hear that your tranny took-sick... I hope it's something minor !

For what it's worth, I had a variety of no-upshift conditions at various times with my New Yorker; one time it was a failing relay (M-5 tranny), then it became a rotted tranny wiring harness that would occasionally ground-out, keep the relay closed and tranny in low, no matter what the road speed or governor status... I finally made-up a new harness, and that put and end to the electrical gremlins. The final episode was when the tranny ate a countershaft gear and some other internals... but I think that was accompanied by some fairly horrific crnuching sounds...

If you didn't hear any munching, it's probably something minor...

Good luck !

Post deleted by psatchwill

On the subject of fluid drive transmissions, I have a 1951 DeSoto six and used to have a 1952 Chrysler New Yorker V8, both fluid drive models. I have driven them, studied them and worked on them. Certainly they are no threat to a modern automatic but they are one of the best efforts at an automatic transmission for their day. They were simple, reliable, worked well, and were not hard to repair or service compared to other automatics of the times.

The fluid coupling would slip at idle but as you speed up the engine it would progressively increase its resistance. Around 1200 RPM you would reach a sort of "irresistable force meets the immovable object" point where the resistance was so high the engine could not overcome it, and you could hold the gas pedal to the floor with the brakes locked and the engine could rev no higher. If it did you knew something was wrong with the fluid coupling.

For speed or racing purposes they used to drain off some of the fluid to allow the engine to rev higher. This had the same effect as a modern day high stall speed torque converter, allowing the engine to rev up into a higher power band.

There is another thing that you can do to speed up the shifts, a simple adjustment. On the carburetor there is an antistall dashpot. Its purpose is to prevent the throttle from closing too quickly which could stall the engine. But the quicker the throttle closes the faster the shift. So you could back off the adjustment in stages until the engine stalls on you when driving, then adjust it up just a little. This would give you the fastest possible shift.

One more old time trick. You can force the shift to go faster. For example if you have the throttle to the floorboards in 3d gear in a drag race and you want to force the shift into high, when you lift off the gas quickly whip the gear lever into low range and back into high and the shift will drop right in.

All this is sort of academic. I am certainly not going to drag race or abuse my car. I know they used to do this in the 50s but come on. Elizabeth Taylor used to ride National Velvet back then too but I doubt she will be jumping on a horse any time soon.

One other thing. A properly adjusted tranny will shift in about one second in normal driving. How fast can you shift a manual trans? I mean a column shift 3 speed from the 40s and early 50s? About the same in normal use. So how slow is the fluid drive really? Or does it just seem slow because you are sitting there doing nothing waiting for it to shift?

I have a technique for driving a fluid drive that works very well and makes it practically the same as driving a modern automatic.

Start the engine with the transmission in neutral, the hand brake applied and your foot off the clutch pedal.

Let the engine warm up until it will idle at its slowest speed.

Depress the clutch pedal shift into gear and release the clutch, all with the handbrake still on.

Release the handbrake and drive away like any automatic. When you get up to 15 MPH lift off the gas and wait for the "click-clunk" and step on it again.

This is very easy, it is based on the owner's manual recommended technique.

You have to drive it more like an automatic, if you drive it like a standard you will hate it. It is not a standard, it is a primitive automatic with a few quirks of its own but with a little understanding your fluid drive or fluid torque drive will work great for you.

Rusty,

I like your explanantion... I wish I'd had a simple tutorial like that when I was learning how to drive my '48 New Yorker !

Yes, driving it per the owner's manual is the "best way"... but I will politely disagree with "driving it like an automatic"... it is not necessary to manipulate the accelerator to "shift" a true automatic tranny ( unless it's tired and slipping)... <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />

When I got my '48 New Yorker running and finally on the road, I had no owner's manual ( had the factory shop manual, but there were no "operating instructions" in it), the internet did not exist then, and I had no "gray-beards" around me who'd had first-hand experience with them "back in the day"... so based on my limited concept from what I could gather from the shop manual, and a few vague references in articles from magazines like Cars & Parts, I ventured-out with my "2-tons of fun" and had to figure it out for myself...

What I eventually learned was that while the tranny does function much like a modern automatic ( Put it in range once, then never touch the shifter or clutch again), the biggest difference

(theoretically and operationally) between true automatics and the MoPar semi-autos is that the driver must release the accelerator for up-shift with the semi-auto.

This is the key to the puzzle... in my case, I was trying to just lighten my foot on the gas pedal... and was frustrated that the car wouldn't up-shift... it wasn't until I was accelerating in low, and lightening (but not removing) my right foot on the accelerator, when I suddenly noticed I was "running out of street", and I took my right foot fully off the gas pedal, to apply the brake... and as if by magic, all of a sudden, there was a "klunk", and I realized that the car had just up-shifted... <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/blush.gif" alt="" /> <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />

It took me another 15-20 minutes of playing around on some side-streets to refine my driving technique a bit (and another couple of years and finally a tear-down of my M-5 to really understand the beast: what it is and how it works), but after that, we got along fine...

The big difference is that the semi-auto ( Presto-Matic, Fluid-Torque, Tip-Toe Shift ) will NOT upshift under load, which true automatic trannys ( Hydramatic, Powerflite, Torqueflite, etc) will do...

Initially, I thought it would suffice just to lighten the foot on the accelerator a bit at shift time, which I was used to doing to help nurse the 2-speed Ford-O-Matic through its upshift in my Dad's very tired '62 Galaxie... if you didn't "help" it upshift, it would slip between low & high, the motor would race, and there would be this horrendous, prolonged shuddering "ooze" into high-speed.

As for "Speed-shifting" the MoPar semi-auto... I gave up on that idea after about a month of regular driving of the car, and just settled-back and "drove it like the book says"... (I eventually DID come-up with an owner's manual from a '46-'48 Winsdor <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />).

And, whether it's by design, or I just have a tired tranny, the regular old three-speed stick on my '41 De Soto ( dry -clutch, no Fluid Drive, or semi-auto) is rather slow to upshift between first and second... I meet some resistance if I try to force the shift faster than it wants to go... there's never any grinding, and my clutch does release fully... it just seems like it prefers to be shifted at a dignified pace... it goes more quickly from 2nd into 3rd, and vice-versa; but there's no rushing that 1-2 up-shift...

Just some of my thoughts on the finer points of MoPar Fluid Drive... it is what it is, and not like anything else one may have driven...

<img src="http://forums.aaca.org/images/graemlins/cool.gif" alt="" />

You are correct about the shifting. I did say "practically the same". The differences are minor, related to using the clutch pedal to put the car in gear when parked, and when shifting from forward to reverse and between low and high range. Plus needing to lift off the gas to upshift.

You are also correct that the typical manual transmission of that day was slow shifting. Blame this on the massive gears and all around massive construction of the transmission plus the heavy flywheels used on all cars back then. They were made so old ladies and grannies of both sexes could drive a standard and get to the grocery store. Today we have automatics for those people and standard transmission cars are more "sporting", plus of course today's engines are so small and lacking in torque that they can get away with a toylike transmission that has very little inertia to overcome.

Rusty,

As I've been getting older, I've been developing more of an appreciation for HOW the automobile and its technologies developed, and it is really interesting how the "modern conveniences" (self-starter, hydraulic brakes, self-shifting & fully automatic trannies, etc) have come to be "standard" on cars...

Chrysler's engineering and design quality were excellent from 1924 though mid-50's at least, but in some areas they seemed to get mired in a particular design ( let's say the fixed-anchor Lockheed brakes) and stuck with it a little too long ( in my humble opinion )...

GM held all the patents on the Hydramatic then, and they weren't sharing... so Chrysler found their own way around the true Hydramatic, sort of making-do with the semi-autos until they developed their own [excellent] auto trannies in the mid-'50s...

In terms of pure mechanical design and function, the planetary transmission of the model T Ford had MUCH more in common with the modern auto-tranny than ANYbody's Rube Goldberg semi-auto: planetary gear reduction/reverse, shifting by bands and disc clutches; the only elements "missing" are the liquid coupling and the automatic shifting device...

Chrysler did do a yeoman's job of developing a reliable sliding-gear manual tranny that would shift gears "by itself" ( well, almost by itself <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" /> )

The one tranny I would now like to figure out is REO's "self-shifter" tranny of 1933-'36... it was some kind of "automatic" tranny, with a push-pull cable-operated shifter handle under the dash, and with a "dry clutch" instead of a fluid coupling... there's not much service text on it in my MoToR's manuals, and so far, I've found no operating guide on it.... ???

Boy, all this talk on the old MoPar semi-auto is really making me yearn to have my New Yorker going again... <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />